The present invention relates to a fiber optic receiver optical sub-assembly (ROSA), and in particular to a high-speed, small form factor ROSA requiring minimal assembly and alignment steps.
Small form factor transceivers are adapted to receive LC optical connectors with a transmitter (Tx) to receiver (Rx) port pitch of 6.25 mm, which is half the standard port pitch distance, 12.5 mm, found in SC transceivers. Conventional small form factor transceivers use Transistor-Outline (TO) can technology for packaging their ROSAs; however, recent demand for small form factor transceivers operating at high bit rates ( greater than 10 Gb/s) have necessitated modifications to the conventional TO can arrangement. Standard photodiodes are packaged along with a pre-amplifier in a TO can package, which is a hermetically sealed unit with a lens in one end for directing incoming light onto the photodiode for conversion of the light into an electrical current. The conventional TO can package implementation of an optical receiver includes four leads, two of which provide transmission of power (Power and Ground) and two of which provide transmission of differential data (Out+ and Outxe2x88x92). Newly developed electro-optic devices, e.g. transceivers, offer diagnostic capabilities, such as optical power monitoring, which includes measuring the power level of the input optical signal. Monitoring the power level of incoming light provides an indication of the quality of the transmitting laser, as well as the incoming transmission line. Accordingly, for newer high-speed ROSAs, the number of leads must be increased to at least six, and the lengths of the leads extending from therefrom must be minimized. Furthermore, the signal path for the electronics must be simplified, and flexible enough, in manufacture, to support both high and lower data rates. Moreover, to minimize costs, the total number of parts must be minimized, and the optical alignment process must be simplified.
An object of the present invention is to overcome the shortcomings of the prior art by providing a relatively simple high-speed small form factor ROSA with the photodiode mounted on the pre-amplifier, which is connected directly to an electrical connector for transmitting electrical signals between the ROSA and the host transceiver.
Accordingly, the present invention relates to a receiver optical sub-assembly (ROSA) for mounting in a host opto-electronic device comprising:
an optical coupler for receiving an optical signal from an optical waveguide along an optical axis;
photodiode disposed along the optical axis for receiving the optical signal and for converting the optical signal into an electrical current signal;
an amplifier for converting the electrical current signal into a differential voltage signal, having the photodiode mounted thereon;
a substrate, a first surface of which is connected to the optical coupler, and a second surface of which supports the amplifier, whereby the optical signal travels from the first surface through the substrate to the photodiode mounted on the amplifier;
an electrical connector connected to the second surface for electrically connecting the photodiode and the amplifier to the host opto-electronic device.